Abstract
Recent seismic tomography unveiled complex mantle plume structures diverging from the originally proposed single, narrow, and vertically-oriented plume conduits, which necessitates new perspectives on the mechanism of hotspot motion. While several recent endeavours have focused on Pacific hotspots' motion, knowledge of others remains limited. Here we constrain the motions of the Kerguelen hotspot within the Indian Ocean by obtaining robust (40)Ar/(39)Ar ages for the Ninetyeast Ridge, Earth's longest linear volcanic ridge. These data indicate varying volcanic progression rates along the ridge, contrasting to a constant rate as previously documented. Combined with constraints on the Indian Plate motion and seafloor spreading, we reveal four periods of motions of the hotspot caused by its interactions with the Indian-Antarctic spreading ridge. This suggests that mantle plume lateral flows are susceptible to changes in shallow mantle convection due to the existence of horizontal ponding zones and vertical conduits, especially in the shallow asthenosphere.